Calling all race cars to the starting line! It’s time to pull out your big box of LEGO bricks to build and race with math fun in mind. You’re going to create a LEGO car that will be powered by a balloon and your own hot air. While it’s easy to construct a LEGO car, the balloon adds a twist that requires problem solving, measurement, and more.
Sit down with your box of LEGO items and grab a few balloons. Blow up one of the balloons to help as you plan your car. You’ll want to get a sense of how long the car needs to be to accommodate the expanded balloon. Measure to see how long the inflated balloon is from top to bottom. Now create a base for your car that is almost the same length. Hint: The thinner pieces work best.
Stop for a moment to chat about factors that make a better race car. Will a heavier or lighter car go faster and further? Test out some options and see which is best. Now use this information to make your car light and stable.
Before putting on the wheels, add an additional brick layer to the base to boost it higher off the ground to prevent the balloon from dragging. This will create friction that slows the car down.
At the rear of your car, create an arch stacked several bricks high with a hole to feed the deflated balloon into. This containment area needs to be high enough so that when you inflate the balloon it will not fall apart –measuring an inflated balloon will help you build it the right size. See the photos for reference.
Your car is almost ready! Can you locate a minifigure to serve as a driver? Next, find a smooth floor like a wood or tile floor for optimal racing conditions. A sidewalk or low-pile carpet will work, but rough surfaces will create more friction under the wheels and that means lower speeds.
Now, position your balloon and blow it up. Pinch the balloon to keep the air in, place the car on the ground, and let it go. Are you happy with the speed and distance of the car? Run a few trials and see if your car needs any adjustments.
If you’re happy with the car, start experimenting to see how the volume of air you put into the balloon changes the speed of the car and the distance it travels. But before you run any time trials, make a few predictions.
A full balloon has a large volume of air. If you have a lot of air packed into the balloon, how will that affect speed and distance?
What if the balloon is barely filled with only a few puffs of air?
I mentioned that a rougher surface will slow the car down, but there’s no need to take my word for it. Make your own predictions and put your car to a real-world test.
Images courtesy of Beth Levine